| 0,0 → 1,83 |
|---|
| """ hmacHash.py |
| |
| Implemention of Request for Comments: 2104 |
| HMAC: Keyed-Hashing for Message Authentication |
| |
| HMAC is a mechanism for message authentication |
| using cryptographic hash functions. HMAC can be used with any |
| iterative cryptographic hash function, e.g., MD5, SHA-1, in |
| combination with a secret shared key. The cryptographic strength of |
| HMAC depends on the properties of the underlying hash function. |
| |
| This implementation of HMAC uses a generic cryptographic 'hashFunction' |
| (self.H). Hash functions must conform to the crypto.hash method |
| conventions and are not directly compatible with the Python sha1 or md5 algorithms. |
| |
| [IETF] RFC 2104 "HMAC: Keyed-Hashing for Message Authentication" |
| |
| >>>key = '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' |
| >>>keyedHashAlg = HMAC(SHA1, key) |
| >>>result = keyedHashAlg(data) |
| """ |
| from crypto.hash.hash import Hash |
| |
| class HMAC(Hash): |
| """ To compute HMAC over the data `text' we perform |
| H(K XOR opad, H(K XOR ipad, text)) |
| """ |
| def __init__(self, hashFunction, key = None): |
| """ initialize HMAC with hashfunction and optionally the key """ |
| # should check for right type of function |
| self.H = hashFunction() # a new instance for inner hash |
| self.H_outer = hashFunction() # separate outer context to allow intermediate digests |
| self.B = self.H.raw_block_size # in bytes, note - hash block size typically 1 |
| # and raw_block_size much larger |
| # e.g. raw_block_size is 64 bytes for SHA1 and MD5 |
| self.name = 'HMAC_'+self.H.name |
| self.blocksize = 1 # single octets can be hashed by padding to raw block size |
| self.raw_block_size = self.H.raw_block_size |
| self.digest_size = self.H.digest_size |
| if key != None: |
| self.setKey(key) |
| else: |
| self.keyed = None |
| |
| def setKey(self,key): |
| """ setKey(key) ... key is binary string """ |
| if len(key) > self.B: # if key is too long then hash it |
| key = self.H(key) # humm... this is odd, hash can be smaller than B |
| else: # should raise error on short key, but breaks tests :-( |
| key =key + (self.B-len(key)) * chr(0) |
| self.k_xor_ipad = ''.join([chr(ord(bchar)^0x36) for bchar in key]) |
| self.k_xor_opad = ''.join([chr(ord(bchar)^0x5C) for bchar in key]) |
| self.keyed = 1 |
| self.reset() |
| |
| def reset(self): |
| self.H.reset() |
| if self.keyed == None : |
| raise 'no key defined' |
| self.H.update(self.k_xor_ipad) # start inner hash with key xored with ipad |
| # outer hash always called as one full pass (no updates) |
| def update(self,data): |
| if self.keyed == None : |
| raise 'no key defined' |
| self.H.update(data) |
| def digest(self): |
| if self.keyed == None : |
| raise 'no key defined' |
| return self.H_outer(self.k_xor_opad+self.H.digest()) |
| |
| from crypto.hash.sha1Hash import SHA1 |
| class HMAC_SHA1(HMAC): |
| """ Predefined HMAC built on SHA1 """ |
| def __init__(self, key = None): |
| """ optionally initialize with key """ |
| HMAC.__init__(self,SHA1,key) |
| |
| from crypto.hash.md5Hash import MD5 |
| class HMAC_MD5(HMAC): |
| """ Predefined HMAC built on SHA1 """ |
| def __init__(self, key = None): |
| """ optionally initialize with key """ |
| HMAC.__init__(self,MD5,key) |